Interstitial lung disease increases mortality in systemic sclerosis patients with pulmonary arterial hypertension without affecting hemodynamics and exercise capacity

Published data suggest that coexisting interstitial lung disease (ILD) has an impact on mortality in patients with systemic sclerosis (SSc) and pulmonary arterial hypertension (PAH), but there is scarce knowledge if this is reflected by hemodynamics, exercise capacity, autoantibody profile, or pulmonary function. In this partially retrospective study, 27 SSc-PAH patients were compared to 24 SSc-PAH patients with coexisting ILD respecting to survival, pulmonary function, hemodynamics, exercise capacity, and laboratory parameters. Survival was significantly worse in SSc-PAH-ILD patients than in SSc patients with isolated PAH (1, 5, and 10-year survival rates 86, 54, and 54% versus 96, 92, and 82%, p = 0.013). Compared to isolated SSc-PAH patients, patients with SSc-PAH-ILD revealed lower forced expiratory volume after 1 s (FEV1) values at the time of PAH diagnosis as well as 1 and 2 years later (p = 0.002) without significant decrease in the PAH course in both groups. At PAH diagnosis, diffusion capacity for carbon monoxide (DLCO) values were lower in the ILD-PAH group. Coexisting ILD was not associated with lower exercise capacity, different FEV1/forced vital capacity (FVC) ratio, higher WHO functional class, or reduced hemodynamics. Higher levels of antibodies against angiotensin and endothelin receptors predict mortality in all SSc-PAH patients but could not differentiate between PAH patients with and without ILD. Our study confirmed an impact of ILD on mortality in SSc-PAH patients. Pulmonary function parameters can be used to distinguish PAH from PAH-ILD. The higher mortality rate cannot be explained by differences in hemodynamics, exercise capacity, or autoantibody levels. Mechanisms of mortality remain to be studied.